Difference between revisions of "UCVM Vs30"

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{| border="1"
 
{| border="1"
! lat !! lon !! Velocity model !! CyberShake-generated Vs30 !! UCVM Vs30 etree.map
+
! lat !! lon !! Velocity model !! CyberShake-generated Vs30 !! UCVM 18.5 Vs30 from Model !! UCVM Vs30 etree.map
 
|-
 
|-
| 34.148426 || -118.17119 || CVM-S4.26.M01 || 838.8 || 748.00
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| 34.148426 || -118.17119 || CVM-S4.26.M01 || 838.8 || || 748.00
 
|-
 
|-
| 34.557 || -118.125 || CVM-S4.26.M01 || 2573.6 ||497.68
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| 34.557 || -118.125 || CVM-S4.26.M01 || 2573.6 || || 497.68
 
|-
 
|-
| 34.0192 || -118.286 || CVM-S4.26.M01 || 313.1 || 280.0
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| 34.0192 || -118.286 || CVM-S4.26.M01 || 313.1 || || 280.0
 
|-
 
|-
| 34.64021 || -118.91919 || CCA-06 || 3393.9 || 748.0
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| 34.64021 || -118.91919 || CCA-06 || 3393.9 || || 748.0
 
|-
 
|-
| 36.13968 || -120.36015 || CCA-06 || 2277.2 || 349.0
+
| 36.13968 || -120.36015 || CCA-06 || 2277.2 || || 349.0
 
|-
 
|-
| 34.26667 || -119.22848 || CCA-06 || 902.3 || 280.0
+
| 34.26667 || -119.22848 || CCA-06 || 902.3 || || 280.0
 
|}
 
|}
  

Revision as of 06:53, 16 May 2018

Introduction

There may be an issue with how UCVM calculates Vs30 values. Presently UCVM uses the following formula:

  1. sum(Vs sampled from [0,30] at 1 meters, for 31 total values) / 31

Rob has suggested that the correct formula should be:

  1. 30 / sum(1 / (Vs sampled from [0, 30) at 1 meters, for 30 total values))

This can have a significant impact for Vs30 calculations. For the BBP1D model, UCVM calculates the Vs30 as 932m/s, whereas Rob's formula calculates it as 862m/s.

Another approach was used in CyberShake Study 15.12, in conversations with Rob:

  1. Vs30 = 30 / Sum (1/(Vs sampled from [0.5,29.5] in 1 meter increments, for 30 total values)).

Points for comparison

We have selected 6 points to compare Vs30 as generated using the CyberShake approach (using half-meters) to other UCVM approaches.

lat lon Velocity model CyberShake-generated Vs30 UCVM 18.5 Vs30 from Model UCVM Vs30 etree.map
34.148426 -118.17119 CVM-S4.26.M01 838.8 748.00
34.557 -118.125 CVM-S4.26.M01 2573.6 497.68
34.0192 -118.286 CVM-S4.26.M01 313.1 280.0
34.64021 -118.91919 CCA-06 3393.9 748.0
36.13968 -120.36015 CCA-06 2277.2 349.0
34.26667 -119.22848 CCA-06 902.3 280.0

= UCVMC Vs30 from etree

-118.1712    34.1484    
-118.1250    34.5570   
-118.2860    34.0192   
-118.9192    34.6402   
-120.3602    36.1397   
-119.2285    34.2667    


UCVMC v18.5 results

-bash-4.2$ ./vs30_query -f ../conf/ucvm.conf -m cvmsi < in.txt
 -118.1712    34.1484    821.328
 -118.1250    34.5570   2573.634
 -118.2860    34.0192    310.574
 -118.9192    34.6402   3393.808
 -120.3602    36.1397   2436.254
 -119.2285    34.2667    283.145


-bash-4.2$ ./vs30_query -f ../conf/ucvm.conf -m cca < in.txt
 -118.1712    34.1484      0.000
 -118.1250    34.5570   2582.267
 -118.2860    34.0192      0.000
 -118.9192    34.6402   3331.251
 -120.3602    36.1397   2279.326
 -119.2285    34.2667    902.013

== Related Links: Plot command used to plot_vs30_map. ./plot_vs30_map.py -b 30.5,-126.0 -u 42.5,-112.5 -s 0.01 -a s -c cs173 -o vs30_cs173.png

Scott posted vs30 values from CyberShake here: http://scec.usc.edu/scecpedia/CyberShake_Study_15.12#Vs_values_v2.0

Example Image: S1252_CCA_depth0_horiz_slice.png


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